title: Protein kinase C plays an important role in the human zona pellucida-induced acrosome reaction.
abstract: To investigate the involvement of protein kinases in signal transduction in the human zona pellucida (ZP)-induced acrosome reaction (AR), the effects of protein kinase (PK) activators, dibutyryl cAMP (PKA) and cGMP (PKG), phorbol 12-myristate 13-acetate (PMA, PKC), and the PKC inhibitor, staurosporine were studied. Sperm samples were obtained from normozoospermic men with normal sperm-ZP binding. Oocytes were obtained from other patients with failure of fertilization in vitro. Motile spermatozoa selected by a swim-up technique were pre-incubated with 2.5-20 microM PMA, 1 mM dibutyryl cAMP or cGMP, 3 mM pentoxifylline or 0.125-2.0 microM staurosporine for 30 min and then incubated with four oocytes for 2 h in human tubal fluid supplemented with bovine serum albumin. The spermatozoa bound to the ZP were dislodged by repeatedly aspirating the oocytes with a small bore pipette and the state of the AR was determined by fluorescein-labelled Pisum sativum agglutinin. Motility and movement characteristics were assessed by computer-assisted sperm analysis (CASA) after incubation of spermatozoa with PMA for 30 min and 2 h. The dibutyryl cAMP and cGMP analogues had a small positive effect (P < 0.05) but pentoxifylline had no effect on stimulating the ZP-induced AR (P > 0.05). In contrast, PMA stimulated ZP-induced AR in a marked dose-dependent manner. Only the highest concentrations (15-20 microM) of PMA significantly decreased percentage motility (P < 0.001). Doses of 2.5-15 microM of PMA significantly stimulated ZP-induced AR without decreasing motility (P < 0.001). The PKC inhibitor, staurosporine (0.125-0.25 microM) significantly inhibited ZP-induced AR without affecting motility (P < 0.001). Sperm samples from 33 normozoospermic men were used for studies of the ZP-induced AR augmented with 15 microM PMA. One sample did not show a response to PMA stimulation. Among the 14 men with low ZP-induced AR, half had normal responses to PMA and other half had low responses to PMA. In conclusion, activation or inhibition of PKC significantly increases or decreases human ZP-induced AR suggesting that PKC plays a important role in the signal transduction pathway for the physiological AR.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Melbourne, Royal Women's Hospital, Carlton, Victoria, Australia.
authors.forename: D Y
authors.initials: DY
authors.lastname: Liu
authors.forename: H W
authors.initials: HW
authors.lastname: Baker
mesh_terms: D000177:Acrosome / Q000201:enzymology / Q000502:physiology*; D003470:Culture Media; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D010431:Pentoxifylline / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015044:Zona Pellucida / Q000201:enzymology / Q000502:physiology*
chemical_list: D003470:Culture Media; D000242:Cyclic AMP; D011493:Protein Kinase C; D006152:Cyclic GMP; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D010431:Pentoxifylline